This invention relates generally to multimedia data, and more particularly to multimedia data embedding.
With the increasingly popularity of multimedia-capable computers, and the digitalization of multimedia in general, the importance of multimedia data embedding has become more important. In one type of multimedia data embedding, a key, also know as a watermark, is embedded into multimedia data, a process which is known as watermarking. This allows questions of ownership of a given piece of multimedia dataxe2x80x94which may be widely distributed by virtue of the Internet, for examplexe2x80x94to be resolved, by attempting to decode the key from the multimedia data. That is, by watermarking multimedia data, the data owner can determine whether a suspect piece of multimedia data is his or hers by determining whether the watermark is present in the suspect data.
For example, a record company, prior to making its music selections available on the Internet for widespread purchase and use, can first watermark the data representing a music selection. If a site on the Internet is providing bootleg copies of the music selections, but claims that the copies are not in fact owned by the record company, the company can prove that they are indeed owned by it by showing that the watermark is present in the bootleg copies. Therefore, watermarking has applicability to audio multimedia, as well as other types of multimedia, such as image and video multimedia.
The invention provides methods for detecting digital watermarks in a media signal and related software implementations. One aspect of the invention is a method of detecting a digital watermark in a media signal. The method computes a weighting function of a digitally watermarked signal. It then applies the weighting function to the digitally watermarked signal to compute a weight-adjusted signal in which parts of the digitally watermarked signal that are more robust to distortion are weighted more than parts that are less robust to the distortion. The method then recovers embedded auxiliary data symbols from the weight-adjusted signal.
Another aspect of the invention is a variation of this first method. This method projects the digitally watermarked signal into a direction according to a key. It then applies a weighting function to the projected signal to compute a projected signal in which parts of the digitally watermarked signal that are more robust to distortion are weighted more than parts that are less robust to the distortion. The method then recovers embedded auxiliary data symbols from the projected signal.
Another aspect of the invention is another variation of the first two methods summarized above. This method projects the digitally watermarked signal into a direction according to a key. It applies a weighting function to the projected signal to compute a projected signal in which parts of the digitally watermarked signal that are more robust to distortion are weighted more than parts that are less robust to the distortion. The method recovers embedded auxiliary data symbols from the projected signal by quantizing the projected signal to determine a binary symbol associated with a quantization of the projected signal.